With the ever-increasing popularity and competitiveness of golf, substantial effort and resources are currently being expended to improve golf clubs. Much of the recent improvement activity has involved the combination of the use of new and increasingly more sophisticated materials in concert with advanced club-head engineering. For example, modern “wood-type” golf clubs (notably, “drivers,” “fairway woods,” and “utility or hybrid clubs”), with their sophisticated shafts and non-wooden club-heads, bear little resemblance to the “wood” drivers, low-loft long-irons, and higher numbered fairway woods used years ago. These modern wood-type clubs are generally called “metalwoods.”
The current ability to fashion metalwood club-heads of strong, light-weight metals and other materials has allowed the club-heads to be made hollow. Use of materials of high strength and high fracture toughness has also allowed club-head walls to be made thinner, which has allowed increases in club-head size, compared to earlier club-heads. Larger club-heads tend to have a larger striking face area and can also be made with high club-head inertia, thereby making the club-heads more “forgiving” than smaller club-heads. Characteristics such as size of the sweet spot are determined by many variables including the shape profile, size, and thickness of the strike plate as well as the location of the center of gravity (CG) of the club-head.
An exemplary metalwood golf club such as a driver or fairway wood typically includes a hollow shaft having a lower end to which the club-head is attached. Most modern versions of these club-heads are made, at least in part, of a light-weight but strong metal such as titanium alloy. In most cases, the club-head comprises a body to which a face plate (used interchangeably herein with the terms “face” or “face insert” or “striking plate” or “strike plate”) is attached or integrally formed. The strike plate defines a front surface or strike face that actually contacts the golf ball.
Regarding the total mass of the metalwood club-head as the club-head's mass budget, at least some of the mass budget must be dedicated to providing adequate strength and structural support for the club-head. This is termed “structural” mass. Any mass remaining in the budget is called “discretionary” or “performance” mass, which can be distributed within the metalwood club-head to address performance issues, for example. Thus the ability to reduce the structural mass of the metalwood club-head without compromising strength and structural support provides the potential for increasing discretionary mass and hence improved club performance.
Some current approaches to reducing structural mass of a metalwood club-head are directed to making at least a portion of the club-head of an alternative material. Whereas the bodies and face plates of most current metalwoods are made of titanium alloy, several club-heads are available that are made, at least in part, of components formed from either graphite/epoxy-composite (or other suitable composite material) and a metal alloy. Graphite composites have a density of approximately 1.5 g/cm3, compared to titanium alloy which has a density of 4.5 g/cm3, which offers tantalizing prospects for providing more discretionary mass in the club-head. Composite materials that are useful for making metalwood club-head components often include a fiber portion and a resin portion. In general, the resin portion serves as a “matrix” in which the fibers are embedded in a defined manner. In a composite for club-heads, the fiber portion may be configured as multiple fibrous layers or plies that are impregnated with the resin component.
For example, in one group of such club-heads a portion of the body is made of carbon-fiber (graphite)/epoxy composite and a titanium alloy is used as the primary face-plate material. Other club-heads are made entirely of one or more composite materials. The ability to utilize lighter composite materials in the construction of the face plate can also provide some significant weight and other performance advantages
To date there have been relatively few golf club head constructions involving a polymeric material as an integral component of the design. Although such materials possess the requisite light weight to provide for significant weight savings, it is often difficult to utilize these materials in areas of the club head subject to the stresses resulting from the high speed impact of the golf ball. The golf club constructions of the present disclosure provide for a golf club which utilizes a lightweight polymeric material in the golf club head allowing for the freeing up of more discretionary weight and further promote performance and adjustability in the resulting golf club head.